Centrifugal pump



Jan. 25, 1966 HIDEKUNI YOKOTA ETAL 3,230,890

CENTRIFUGAL PUMP 5 Sheets-Sheet 1 Filed NOV. l5 1963 FIG.

Jam 25, 1966 HIDEKUNI YOKOTA ETAL 3,230,890

CENTRIFUGAL PUMP 5 Sheets-Sheet 2 Filed NOV. l5, 1963 FIG. 5

Jan. 25, 1966 HIDEKUNI YoKoTA ETAL 3,230,890

CENTRIFUGAL PUMP 5 Sheets-Sheet 5 Filed NOV. l5, 1963 FIG. 8

FIG. 6

FIG. 7

United States Patent O 3,230,890 CENTRIFUGAL PUMP HidekuniYokota, 671Yoshijima-ho, and Shingo Yokota,

" 1627 Midori-machi, both of Hiroshima-shi, Japan Filed Nov. 15, 1963,Ser. No. 324,065 Claims`priority, application Japan, Nov. 20, 1962,37/52,2`59; Mar. 23, 1963, 38715329 2 Claims. (Cl. 1113-113) Thisinvention relates to centrifugal pumps and more particularly to a newcentrifugal -pump suitable for pumping high-viscosity, mud-like fluids`containing large amounts of -lbulbble's. t l

The pumping of high-viscosity, mud-like fluids containing largeainounts-of-'bubbles by means .of centrifugal pumpsis generallyconsidered to'be'- extremely difficult.

Atthe same time, thereis `a great demand for -a simple,

' safe, and reliable'means for pumping such muddy uids containingadditional foreign solid matter.

It has been found that'the reason for this difficulty ofcentrifugalipump Acombined with a vacuum creating means whereinthe-*ingress of the fluid into lthe vacuum creating means is'eifectivelyprevented.

`According to the present 'invention, there is provided a centrifugal'pump (referredto hereinafter as the main pump); adapted for pumping ofthe above mentioned muddyi-fluid, and in sideby-,side relation to themain pump is arranged v'another centrifugal pump (referred to"hereinafter as vthe auxiliary pump) for drawing vair .avities in themain pump. The auxiliary pump is, through 'the suction inlet thereof, incommunication with the cejntralarea of the. main pump chamber and is,throughfhe discharge outlet thereof, in communication with'thesuctioninlet of the .main pump. The central area of the auxiliary pumpchamber is lin communication with a suitable vacuumcreating meansthrough a suction passage,fso' ,that,airfcavities in-the main pumpchamber will `betfdrawn intofand forced through vthe auxiliary pumpchamber. to the vacuumcreating means in order to ensure acontinuousfiuid-iiow through the main pump chamber.f. f.

Accordingto another object of this invention, there is. provided a valveymeansbetween the auxiliary pump and the .vacuum creating means, whichvalve means is constructed soas to open the suction passage from theauxiliary pump to the-vacuum creating means when the vacuum creatingmeans is operative and to close the samewhen the'vacuum creating meansis inoperative, thus preventing ingress of fluid to the vacuum creatingmeans.v Y

The nature, principles, and details of the invention, as well as otherobjects and features thereof, will be more 'cl'ea'rly apparent fromthefollowing description taken in connection with the accompanyingdrawings in which like parts are designated by like referencecharacters, and in which:

FIG. 1 is a side elevational view, partly in vertical materials.

ICC

section, showing a prefered embodiment of the centrifugal pump of thisinvention;

FIG. 2 is a section taken along the line II-II of FIG. l, the Viewlooking in the direction of the arrows;

FIG. 3 is a section taken along the line IIL-III of FIG. l, the viewlooking in the direction of the arrows;

FIG. 4 is a side elevational View, partly in vertical section, showing amodified centrifugal'pump according to this invention;

FIG. 5 is a section taken along the line V-V ofFIG. 4, the viewlookingin the direction of the arrows;

FIG.6 is a section taken along the line VI-VI of FIG. 4, the viewlooking in the direction of the arrows;

FIG. 7 is a section taken -along the line VII--VII .of

FIG. 4, the view looking in the direction of the arrows;

l and charge outlet 5, which communicates with the .suctionV inlet 3 ofthe main pump A through a connecting pipe 8 and a' return passage 7leading into the suction inlet 3:.I Within the main pump casing 1 thereis an impeller 9-provided with blades 11 and theimpeller 9 is mounted ona driving shaft 10. The impeller 9 is shown as ibeing of open typehaving no shroud but the impeller may 4be of'any known type accordingto' the nature of fluid to'be treated. Between the main pump casing 1`andthe auxiliary pump casing 2 there is disposed a partition plate 6serving as side walls of both the main and auxiliary pump casings. Thepartition plate 6 is provided with a centrally cut opening through whichthe driving shaft 10 extends. The opening of the partition plate 6 isvso formed that the diameter thereof is slightly larger' than that ofthe shaft 10 and increases gradually toward the auxiliary pump B. Thus,it Will be apparent that a gap 13 between the'outer face of the impellerhub and the inner surface of the opening of the partition plate 6 isgreater on the side of the auxiliary pump B and smaller on the side ofthe main pump A. The

tapered form of vthe gap 13 serves to prevent the gap from` beingclogged with foreign matter. The vmembers which form the gap 13 may bemade of a combined hard material and rubber to increase theirdurability, or may be provided with teeth to crush foreign matter andfibrous In'any case, it is necessary to suitably throttle the inlet ofthe auxiliary pump Bat the gap 13 in relation to the pumping capacity ofthe auxiliary pump B.

Within the auxiliary pump casing 2 there is an impeller 14 havingtherethrough openings 15 in the central portion thereof and the impeller14 is also mounted on the driving shaft 10. The auxiliary pump casing 2has an air suction passage 16 which extends from the central portion ofthe auxiliary pump vB so as to communicate with an intake 17 of a vacuumpum-p 18, which is driven by the driving shaft 10 together with theimpellers 9 and 14. About the driving shaft 10 there is provided astuffing box 19 containing sealing material 20 therein.

In operation, when the pump is driven with the discharge outlet 4thereof closed, the air on the suction side of the main pump is drawninto the vacuum pump 18 through the inlet 3, the impeller 9, the gap 13,the impeller 14, the passage 16, and the intake 17 of the vacuum pump18, and at the same time through the inlet 3, the return passage 7, theconnecting pipe 8, the discharge outlet 5 of the auxiliary pump B, theimpeller 14, the passage 16, and the intake 17 of the'vacuum pump 18.Thus, the vacuum established in the pum-p chamber causes vthe luid to betreated `to ow into the suction inlet 3 and thence into the chamber ofthe main pump A so as to fill' the chamber. The uid thus introduced intothe chamber of the main pump A tends to advance to iill the returnpasage 7, the connecting pipe 8, and the discharge outlet 5 of theauxiliary pump B, and reach the chamber of the auxiliary pump B.However, the auxiliary pump B is so designed that the impeller 14thereof may operate to overcome the vacuum developed by the vacuum pump18, and, therefore, the pump B prevents the fluid from being drawn fromthe pasage 7 to the auxiliary pump B, thereby functioning as a kind ofcheck valve.

Thus, thefluid in the chamber of the main pump A ows through the gap 13into the auxiliary pump B, and

thence through the discharge outlet 5 and the returnv pasa'ge 7 back tothe chamber of the main pump A because of the fact that the gap -13which is an inlet of the auxiliary pump B is throttled.

It will be apparent, therefore, that the fluid introduced into theauxiliary pump chamber never flows into the air suction passage 16, andthe vacuum pump 18 is maintained free of the fluid.

When the uid contains much air, it is introduced into the main pump Awith a number of cavities. Under such a condition, the cavities areexpelled from the main pump chamber through the gap 13 into theauxiliary pump chamber. The auxiliary pump, being'also a strongcentrifugal separator, centrifugally separates the air from the duid anddelivers the remaining fluid from therv discharge outlet 5 back to themain pump A, thus attaining a continuous and reliable pumping operation.The openings 15 serve vto pass the cavities from the gap 13 to thepassage 16.

In the practical use of the pump as described above, in case anequipment havinga positive suction head is adopted and the viscosity ofthe liquid to be treated is not high, a particular vacuum pump is notnecessary. In this case, it is only necessary to lead the air suctionpassage 16 up to a position higher than the liquid suction level bymeans of a pipe -device and more favorable eifects can be expected byproviding a check valve adapted to check suction of the externalatmosphere into the passage at the extreme or intermediate portion ofthe passage.

Referring now to FIGS. 4 to 8, there is shown a modied form of the pumpaccording to this invention. The construction of this modified form issubstantially the same as that shown in FIGS. 1 to 3 with the exceptionthat the modified pump is provided with a safety valve 21 which isinserted between the air suction passage 16 and the intake 17 of thevacuum pump 18 and may be positioned on the casing of the pump. Theembodiment illustrates a particular exam-ple in which a semi-open typeimpeller and a special contrivance adapted to decrease `cavitation atthe back surface of the blades are provided. In other words, at theshroud of the impeller, a slit 12 is provided along the back surface ofeach blade 11 so that the inside end portion of the slit 12 faces thegap 13. Accordingly, the back surfaces of the blades 11 are always indirect communication with the vacuum pressure of the vacuum pump. Thesafety valve 21 includes a valve casing 22, which has in the bottomplate thereof an opening 23 in which is fitted a valve seat 24. Thevalve casing 22 is also provided in the side wall thereof with a port 25communicating with the intake 17 of the vacuum pump 18. In the upperpart of the casing 22 there is a diaphragm 26 extending transverselythereacross and secured at its periphery to the casing 22 in air tightrelation thereto. A cover 27 is secured to the upper end of the casing22, and the cover 27 is provided with an opening 28. Immediately underthe diaphragm 26, there is a valve rod 29 which extends ve-rtically andcentrally through the casing 22 and which is supported by a support 30for permitting vertical movement. The valve rod 29 is always urgedupwardly by a coil spring 31 and is provided at the lower end thereofwith a valve head 32 abuttingly engageable with the valve seat 24. Thecoil spring 31 is so designed that when the pressure in the valve casing22 is equal to the external atmospheric pressure, that is, when thevacuum pump is inoperative, the valve head 32 is in con-tact with thevalve seat 24. The diaphragm 26, in practice, may be replaced by'other'equivalent means such as a bellows or piston. l

The pump described above in connection with FIGS. 4 to 8 is suitable foruse'in the case where the level of fluid to be pumped is higher thanthat of the pump. Then, when the pump is inoperative, the fluid to betreated is caused to ow into the pump chamber. However, the rise of Vthefluid level in the auxiliary pump chamber is limited because the valve21 1closes the passage 16, thus causing air to be coniined in the upperpart ofthe passage 16.

In operation, when the pump is started, the fluid flows from the mainpump chamber through the throttled gap 13 linto the auxiliary pumpchamber,l whilethe fluid in the air suction passage 16 is delivered tothe discharge out. let 5 of the auxiliary pump B by the rotatingimpeller 14 thus flowing back to the main pump chamber through thereturn passage 7. In such a condition, the 4rotating impeller 14 of theauxiliary pump B holds air cavities near the central portion thereof. ,Yl v When the pressurein the valve casing 22 decreases because of theoperation ofthe vacuum pumpv18, the diaphragm 26 is displaced downwardbyatmospheric pressure to cause the rodr29,to move downward againstrtheforce of the spring 31, thereby permitting the valve 21 to open, wherebythe pressure in t-he passage 16 is decreased together with the pressuresin the central parts of the main and auxiliary pumps A and B. Thus, therequired pumping oper-ation is accomplished.

If air cavities are formed in t'hercentr'al rarea of the main pumpchamber by the introduction of air-containing fluid, they will beexpelled into theauxiliary 'pump cham` ber and thence into the airsuction passage 16. The auxiliary pump B of` this example is also ofsuch `design that the` impeller 14 thereof umay operate to overcome thevacuum developed by the vacuum pump 18. Therefore,` the fluid beingtreated is prevented from entering into y' is not used. The ingress offluid into the"vacuurnfpu'mpV 18 is undesirable and will always causepump failure if fit is of a nature harmful to this pump.

, While we have disclosed preferred embodiments of this invention, it isto be understood that various changes and modifications may bemadetherein without departing fromy the spirit and scope of lthisinvention. For example, there lmay be` provided a'oat valve in the airsuction passage 16 for preventinguundesirable'ingress ofthe fluid intothe vacuum pump 18 inthe vcase ofdamage to the impeller 14 or of pumpstoppage. The suction line between the air suction passage '16 andtheintake 17 of the vacuum pump 18 may have a fluid sumpwith a check valvefor fluid disposal at the bottom thereof for the sake of safety.Furthermore, the auxiliary .pump impeller 14 may have two impellerplates for eicient centrifugalseparation of uid from air, and theopenings 15 provided in the impeller 14 may be arranged eccentricallyand in a staggered state.

What we claim is: Y H D 1. A centrifugal pump assemblage comprising amain pump having a casing, a driving shaft,`a main` centrifugal impeliermounted on said shaft within the casing,l a suction inlet and adischarge outlet communicating with said casing,an auxiliary pump havingan auxiliary casing disposed in side-by-side relationship to the mainpump casing, a common wall between said main and auxiliary casings, anauxiliary centrifugal impeller, said driving shaft extending through theauxiliary pump casing and through said common wall, said auxiliaryimpeller being mounted on said shaft within said auxiliary pump casing,said common wall having a central suction inlet opening thereinproviding communication between said main pump casing and said auxiliarypump casing, means on said shaft serving to restrict the cross sectionalarea of said central suction inlet opening, a discharge outlet from saidauxiliary casing communicating with the suc tion inlet of the main pumpcasing, whereby dense tluid is discharged from said auxiliary pumpcasing to the suction inlet of said main pump casing, and a vacuum pumphaving a suction inlet in communication with said auxiliary pump casing,whereby gaseous medium is withdrawn from said auxiliary pump casing, thepumping capacity of the vacuum pump being such that the vacuum developedthereby is overcome by the pumping action of the auxiliary pump.

2. A centrifugal pump assemblage comprising a main pump having a casing,a driving shaft, a main centrifugal impeller mounted on said shaftwithin the casing, a suction inlet and a discharge outlet communicatingwith said casing, an auxiliary pump having an auxiliary casing disposedin side-hy-side relationship to the main pump casing, a common wallbetween said main and auxiliary casings, an auxiliary centrifugalimpeller, said driving shaft extending through the auxiliary pump casingand through said common wall, said auxiliary impeller being mounted onsaid shaft within said auxiliary pump casing, said common wall having acentral suction inlet opening therein providing communication betweensaid main pump casing and said auxiliary pump casing, means on saidshaft serving to restrict the cross sectional area of said centralsuction inlet opening, a discharge outlet from said auxiliary casingcommunicating with the suction inlet of the main pump casing, wherebydense Huid is discharged from said auxiliary pump casing to the suctioninlet of said main pump casing, a vacuum pump having a suction inlet incommunication with said auxiliary pump casing, whereby gaseous medium isWith drawn from said auxiliary pump casing, the pumping capacity of thevacuum pump being such that the vacuum developed thereby is overcome bythe pumping action of the auxiliary pump, and valve means in the suctioninlet between the auxiliary pump and vacuum pump, said valve means beingopenable in response to the operation of the vacuum pump.

References Cited by the Examiner UNITED STATES PATENTS 3,073,249 1/1963Yokota et al 103-113 FOREIGN PATENTS 556,579 8/ 1932 Germany. 614,571 6/1935 Germany.

22,806 3/ 1962 East Germany. 499,220 6/ 1930 Germany.

SAMUEL LEVINE, Primary Examiner.

HENRY F. RADUAZO, Examiner.

1. A CENTRIFUGAL PUMP ASSEMBLAGE COMPRISING A MAIN PUMP HAVING A CASING,DRIVING SHAFT, A MAIN CENTRIFUGAL IMPELLER MOUNTED ON SAID SHAFT WITHINTHE CASING, A SUCTION INLET AND A DISCHARGE OUTLET COMMUNICATING WITHSAID CASING, AN AUXILIARY PUMP HAVING AN AUXILIARY CASING DISPOSED INSIDE-BY-SIDE RELATIONSHIP TO THE MAIN PUMP CASING, A COMMON WALL BETWEENSAID MAIN AND AUXILIARY CASINGS, AN AUXILIARY CENTRIFUGAL IMPELLER, SAIDDRIVING SHAFT EXTENDING THROUGH THE AUXILIARY PUMP CASING AND THROUGHSAID COMMON WALL, SAID AUXILIARY IMPELLER BEING MOUNTED ON SAID SHAFTWITHIN SAID AUXILIARY PUMP CASING, SAID COMMON WALL HAVING A CENTRALSUCTION INLET OPENING THEREIN PROVIDING COMMUNICATION BETWEEN SAID MAINPUMP CASING AND SAID AUXILIARY PUMP CASING, MEANS ON SAID SHAFT SERVINGTO RESTRICT THE CROSS SECTIONAL AREA OF SAID CENTRAL SUCTION INLETOPENING, A DISCHARGE OUTLET FROM SAID AUXILIARY CASING COMMUNICATINGWITH THE SUCTION INLET OF THE MAIN PUMP CASING, WHEREBY DENSE FLUID ISDISCHARGED FROM SAID AUXILIARY PUMP CASING TO THE SUCTION INLET OF SAIDMAIN PUMP CASING, AND A VACUUM PUMP HAVING A SUCTION INLET INCOMMUNICATION WITH SAID AUXILIARY PUMP CASING, WHEREBY GASEOUS MEDIUM ISWITHDRAWN FROM SAID AUXILIARY PUMP CASING, THE PUMPING CAPACITY OF THEVACUUM PUMP BEING SUCH THAT THE VACUUM DEVELOPED THEREBY IS OVERCOME BYTHE PUMPING ACTION OF THE AUXILIARY PUMP.